CA1299203C

CA1299203C - Process for producing ethylene dichloride

Info

Publication number: CA1299203C
Application number: CA000554445A
Authority: CA
Inventors: Christoph Buhs; Garnet E. Mcconchie; Eberhard Dreher
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1987-01-03
Filing date: 1987-12-16
Publication date: 1992-04-21
Anticipated expiration: 2009-04-21
Also published as: EP0275537B1; YU240587A; US4849562A; DE3700132A1; JPH0223533B2; DE3761019D1; CN87107411A; CN1010009B; DE3700132C2; AU1002988A; KR880008967A; AU596486B2; EP0275537A1; KR900006905B1; JPS63215648A

Abstract

ABSTRACT

PROCESS FOR PRODUCING ETHYLENE DICHLORIDE

The oxychlorination process for producing ethylene dichloride is carried out by reacting ethylene with hydrogen chloride and oxygen in an oxychlorination reactor. Thereby, ethyl chloride and perhaps vinyl chloride are produced as by-products. The effluent from the reactor is at least fractionated into an ethylene dichloride-rich fraction (I) and an ethyl chloride-rich fraction (II) so that fraction (I) contains less than 50 percent of the total weight of ethyl chloride produced in step a) and the sum of the weight of ethylene dichloride and vinyl chloride in fraction (II) is less than 30 percent of weight of ethyl chloride in fraction (II). The ethyl chloride-rich fraction (II) is subjected to a cracking reaction in the presence or absence of an inert diluent wherein ethyl chloride is converted into ethylene and hydrogen chloride in the presence of a catalyst. The total weight of ethylene dichloride and vinyl chloride is less than 5 percent, based on the combined weight of ethyl chloride and any inert diluent. This process provides an improved means for handling by-products of ethylene dichloride production.

Description

~299203 PROCESS FOR PRODUCING ETHYLENE DICHLORIDE
Background of the Invention The present invention relates to a process for producing ethylene dichloride. More specifically, it relates to an oxy-chlorination process in which ethylene is reacted with hydrogen chloride and oxygen in the presence of a catalyst.
1,2-dichloroethane (ethylene dichloride) is used exten-sively for producing vinyl chloride.
Accordingly, intensive research has been made by those skilled in the art relating to the production of 1,2-dichloro-ethane. A process which is widely used in industry is the oxy-chlorination process in which ethylene is reacted with oxygen and hydrogen chloride in the presence of a catalyst such as copper dichloride. Extensive patent literature exists relating to the catalysts in the process and to the process technologies which, among others, try to maximize yield of ethylene dichloride. The by-products from existing processes are usually burnt and hydrogen chloride is recovered. Although the yield of ethylene dichloride is quite high, generally between 90 and 97 percent, depending on the process type and conditions, the incineration of the by-products in large scale production is a problem for the environ-ment.
European patent 0 005 655 suggests oxidative destruction of the by-products using a catalyst containing platinum or iridium on a support of alumina having the eta crystallographic structure to improve the incineration process.

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~299XO~

However, incineration of the by-products remains unecon-omical and efforts are necessary in order to keep the pollution of the environment to a low level.
In European patent application 0 132 971 an oxychlorina-tion process is disclosed wherein hydrogen chloride gas and oxygen are reacted with an unsaturated organic compound. Chlorine con-taining organic residues are combusted in an oxygen-rich flame whereby hydrogen chloride is produced which is recycled to the oxychlorination process. However, this process is rather incon-venient because a high combustion temperature of more than 2000Cis required to ensure complete destruction of the residuesO
European patent application 0 132 971 discloses that steps must be taken to avoid corrosion of the chamber material in the presence of hydrogen chloride.
In the German Auslegeschrift DE-AS-24 00 417 it is suggested to adsorb the by-products of the oxychlorination process partially on activated carbon and to burn the non-adsorbed by-products such as ethylene at a temperature between 500C to 2000C. The adsorbed impurities such as ethylene dichloride and ~0 ethyl chloride are then desorbed with vapour.
However, a careful separation of vapour and chlorinated by-products is required after the desorption step in order to avoid pollution of water.
Accordingly, it would be desirable to overcome these disadvantages of known oxychlorination processes for producing ethylene dichloride.

X

~299203 It has been found that the problem of by-products dis-posal can be reduced by separating ethylene dichloride and ethyl chloride (which is one of the main by-products in the oxychlorina-tion process) and then converting ethyl chloride to ethylene and hydrogen chloride in the presence of a catalyst.
Summary of the Invention The present invention is an oxychlorination process for producing ethylene dichloride by a) reacting ethylene with hydrogen chloride and oxygen in the presence of an oxychlorination catalyst in an oxychlorination reactor, whereby ethyl chloride or both ethyl chloride and vinyl chloride are produced as by-products which process is characterised in that it comprises the further steps of b) dividing, in one or more steps, the effluent from the oxy-chlorination reactor into at least i) an ethylene dichloride-rich fraction (I) and ii) an ethyl chloride-rich fraction (II) in such a fashion that fraction (I) contains less than 50 percent of the total weight of ethyl chloride produced in step a) and the sum of the weight of ethylene dichloride and vinyl chloride in fraction (II) is less than 30 percent of the weight of ethyl chloride in fraction (II) and c) subjecting fraction (II) to a cracking process in the presence or absence of an inert diluent whereby fraction (II) contains less than 5 percent ethylene dichloride and vinyl chloride based on the combined weight of ethyl chloride and inert X

diluent in fraction (II) prior to cracking, the cracking pro-cess is carried out in the presence of a cracking catalyst in a cracking reactor and ethyl chloride is converted into ethy-lene and hydrogen chloride.
From Kirk-Othmer "Encyclopedia of Chemical Technology"
3rd edition, 1979, vol. 5, page 715, G.M. Schwab and H. Noller, z.Eletrochem. 58, 762 (1954) and A. Heinzelmann et al., J.
Monatsh. Chemie 102, 1750 (1971) it is generally known that ethyl chloride is decomposited to ethylene and hydrogen chloride at about 300C in the presence of certain cracking catalysts. How-ever, these references do not suggest anywhere to use a cracking step in the oxychlorination process. The skilled artisans have concentrated on incineration methods for disposing of the by-products in the oxychlorination process.
Surprisingly, it has been found that a good conversion rate of ethyl chloride to ethylene can be achieved in the process of the present invention and that unconverted ethylene from the oxychlorination step a) does not substantially affect the conver-sion rate in step c).
The oxychlorination process of the present invention is useful for producing ethylene dichloride on a large scale. The process of the present invention allows a substantial saving of ethylene which is used as raw material but which is expensive. By the present invention the yield of produced ethylene dichloride, based on the amount of ethylene consumed, can be increased by 1 to 2 percent. Depending on the process conditions, even 1.5 to 2 X

percent yield increase can be achieved.
The drawing illustrates a flow sheet of one embodiment of the process of the present invention~
Detailed Description of the Invention Process step a) is well known in the literature. A
general description of the oxychlorination reaction is published in ULLMANNS Enzyklopadie der technischen Chemie, 4th Edition, volume 9, pages 428 to 431. A preferred process step a) is des-cribed in U.S. patent 3,184,515.
Ethylene is reacted with hydrogen chloride and oxygen in the presence of an oxychlorination catalyst. The typical molar ratios of hydrogen chloride : oxygen : ethylene used in industry are from 1.8 to 3 moles, preferably from 1.9 to 2.4 moles hydrogen chloride and from 0.4 to 0.7 moles, preferably from 0.5 to 0.6 moles oxygen per mole ethylene.
Ethylene may originate from hydrocarbon cracking facili-ties and may contain usual impurities such as methane, ethane and other hydrocarbons.
The oxychlorination step a) may be carried out in liquid phase in which the catalyst is dissolved. In a liquid phase re-action the temperature is preferably from 150C to 200C, more preferably from 170C to 190C and the pressure is preferably from 13 to 22 bar, more preferably from 15 to 20 bar.
However, a gaseous phase oxychlorination is preferred for the purpose of the present invention. In general, the temper-ature in the gaseous phase oxychlorination process is from 200C, X

preferably from 210~C and more preferably from 230C and up to 450C, preferably up to 350C and more preferably up to 280C. In general, the pressure is from 1 bar, preferably from 2 bar and more preferably from 3 bar, up to 10 bar, preferably to 8 bar, more preferably to 7 bar.
Useful oxychlorination catalysts for the purpose of the present invention are also known. A preferred catalyst is copper(II) chloride. Copper(II) chloride can be used together with alkali or alkaline earth metal chlorides, for example potas-sium chloride. The copper chloride catalyst can be deposited on aconventional carrier material such as high surface aluminum oxides, preferably gamma-alumina, silica, celite or zeolites.
Well known reactor types are useful for the purpose of the present invention, such as fixed bed reactors or fluidized bed reactors.
Since the oxychlorination reaction is highly exothermic, efficient temperature control is necessary. In the gas phase reaction, it is preferred to dilute the reactive gases with one or more inert gases such as nitrogen. Dilution may also be achieved by using air as the oxygen source in the oxychlorination process.
When using air in a continuous oxychlorination process, excess nitrogen is removed from the reactor in order to avoid a pressure build up. Preferably, the oxychlorination process is carried out by continuously feeding oxygen into the reactor and by diluting it with nitrogen which is continuously recycled into the oxychlorina-tion reactor after the reaction.

The mixture produced in the oxychlorination reactor is removed from the reactor and preferably cooled to a temperature of less than 200C, more preferably to a temperature between 20C and 160C, preferably at a pressure of from 1 to 10 bar, more prefer-ably from 2 to 8 bar. It is advisable to remove residual amounts of unreacted hydro~en chloride from the mixture produced in -the oxychlorination reactor, for example by washing it with hot water, a hot alkaline solution such as aqueous sodium hydroxide or with both. The washing of hydrogen chloride is preferably carried out at a temperature of less than 200C, more preferably less than 150C and a pressure of 1 to 5 bar. The amount of ethyl chloride produced in the oxychlorination step a) depends of course on the reaction conditions. In general, it is between 1 to 3 percent, based on the weight of produced ethylene dichloride.
In process step b) the effluent from the oxychlorination reactor, from which excess hydrogen chloride preferably has been separated, is divided in one or more steps into at least i) an ethylene dichloride-rich fraction (I) and ii) an ethyl chloride-rich fraction (II). Preferred fractionation steps are described in more detail below wi-th respect to the drawing.
In order to reach a substantial process improvement, the ethylene dichloride-rich fraction (I) should contain less than 50 percent, preferably less than 30 percent, more preferably less than 20 percent of the total weight of ethyl chloride which has been produced in step a). Less efficient fractionation is pos-sible but renders the process uneconomical. At least 50 percent, X

lZ99Z03 preferably at least 70 percent, most preferably at least 80 per-cent of the total weight of ethyl chloride produced in step a) is subjected to cracking step c).
In the ethyl chloride-rich fraction (II), the total amount of ethylene dichloride and vinyl chloride (which is often produced as a by-product in oxychlorination) is less than 30 per-cent, preferably less than 10 percent and more preferably less than 5 percent, based on the weight of ethyl chloride.
In general, the presence of ethylene dichloride or vinyl chloride decreases the lifetime of the catalyst in cracking step c), however the presence of unreacted ethylene does not signifi-cantly affect the cracking step c). For example, the ethyl chloride-rich fraction (II) may contain an ethyl chloride/ethylene molar ratio of 1:1 to 5:1 without significant impact on the crack-ing reaction. The ethyl chloride-rich fraction (II) is then fed to a cracking reactor.
It is preferred to carry out cracking step c) in the presence of an inert diluent. It has been found that the lifetime of the catalyst and the conversion of ethyl chloride can be in-creased in the presence of an inert diluent such as nitrogen. Themolar ratio between the inert diluent and ethyl chloride is pre-ferably from 0.25:1, more preferably from 0.5:1, most preferably from 0.75:1, up to 30:1, preferably up to 20:1, more preferably up to 15:1. The combined amount of ethylene dichloride and vinyl chloride in the fraction (II) is less than 5 weight percent, pre-ferably less than 4 weight percent and more preferably less than X

1;;:99203 3 weight percent, based on the combined weight of ethyl chloride and any inert diluent present in the fraction (II). If the com-bined amount of ethylene dichloride and vinyl chloride in fraction (II) is more than 5 percent of the ethyl chloride weight in frac-tion (II), a diluent has to be added.
The cracking reaction c) is carried out at a suitable pressure and temperature. The cracking reaction c) is generally carried out at a temperature between 150C, preferably between 200C, most preferably between 250C, and 450C, preferably 350C, most preferably 320C. The conversion of ethyl chloride increases with increasing temperature. Depending on the temperature in the reactor, a pressure preferably between 1 and 8 bar, more prefer-ably between 1 and 5 bar, most preferably between 1 and 3 bar is maintained. The conversion of ethyl chloride to ethylene and hydrogen chloride increases with decreasing pressure, but vacuum operation is inconvenient in large scale cracking reactors.
The preferred residence time of ethyl chloride in the cracking reactor depends on several factors such as temperature and desired conversion rate. In general, a suitable residence time is from 2 sec., preferably from 3 sec., more preferably from 5 sec. and up to 120 sec., preferably up to 60 sec., more prefer-ably up to 45 sec. Reasonable conversion rates are achievable at a residence time of 30 sec. or less.
Useful cracking catalysts for process step c) are those which are generally known for cracking hydrocarbons, for example zeolite and silicalite catalysts. Preferred catalysts are g aluminum oxide in various configurations, of which gamma-alumina is preferred. Gamma-alumina which has a surface area between 10 m2/g, preferably between 50 m2/g, more preferably between 100 m2/g and 350 m2/g, preferably 320 m2/g, more preferably 250 m2/g is preferred. It has been found that gamma-alumina which has a sur-face area between 50 m2/g and 250 m2/g and correspondingly a rela-tively large pore diameter, and which contains low levels of im-purities such as Na2O and SiO2, is relatively insensitive to re-actant feed impurities such as ethylene dichloride and vinyl chloride. Only a few by-products are produced in the cracking reaction c) when using these reaction catalysts. Preferably, the average pore diameter of the gamma-alumina is 3 to 30 nm, more preferably 6 to 20 nm. The level of impurities, such as ~a2O and sio2, is preferably less than 15,000 ppm, more preferably less than 10~000 ppm, most preferably less than l,000 ppm, based on the weight of gamma-alumina.
The effluent from the cracking reactor contains mainly ethylene and hydrogen chloride, inert diluent, if present, and minor amounts of impurities such as non-converted ethyl chloride.
This effluent mixture can be treated as described below with reference to the drawing.
One preferred embodiment of the invention is explained in detail with reference to the drawing. In respect to said draw-ing, via lines l, 2, 3 ethylene, hydrogen chloride and oxygen are fed to the oxychlorination reactor A in which ethylene is convert-ed to 1,2-dichloroethane (ethylene dichloride) as described above ~299Z03 ~ 72425-5 (process step a). The temperature of ethylene, hydrogen chloride and oxygen to be fed is preferably from 180 to 400C, more prefer-ably from 200 to 380C. The pressure in lines 1, 2 and 3 is pre-ferably from 1 to 10 bar, more preferably from 2 to 8 bar. Nitro-gen is generally used as an inert diluent for the reaction and is fed to the oxychlorination reactor A in the amount desired.
The effluent 4 from the oxychlorination reactor A is preferably cooled and excess hydrogen chloride is preferably removed from the effluent as described above with respect to the oxychlorination step a). The effluent 4 then contains 1,2-di-chloroethane and by-products.
The main by-product is ethyl chloride. Other by-products which are ordinarily found in effluent 4 are water, carbon dioxide, carbon monoxide and vinyl chloride. The effluent 4 further contains unreacted ethylene and any inert diluent. It may also contain trichloromethane and minor amounts of other impurities.
The effluent 4 from the oxychlorination reactor A is separated, preferably by condensation, into a gas fraction 6 and a liquid fraction 5. The fractionation bl) is carried out in frac-tionation equipment Bl, preferably in a condenser. The tempera-ture in the fractionation equipment Bl, in the gas fraction 6 and in the liquid fraction 5 is preferably from 20C to 120C, more preferably from 30C to 100C. The pressure in the fractionation equipment Bl is preferably from 1 bar to 10 bar, more preferably from 2 bar to 8 bar.

Gas fraction 6 contains mainly the inert diluent(s), carbon dioxide, carbon monoxide, non~converted ethylene and imp-urities. Preferably, gas fraction 6 is recycled to the oxychlori-nation reactor A.
The liquid fraction 5 consists mainly of 1,2-dichloro-ethane but also contains the major by-product ethyl chloride and minor amounts of other by-products such as vinyl chloride, water and/or trichloromethane, and of unconverted ethylene.
In the second fractionation equipment B2, liquid frac-tion 5 is separated in a fractionation step b2) into a 1,2-di-chloroethane fraction 8 and a by-product fraction 7, preferably by distillation. The temperature of the distillation is preferably from 30C to 180C, more preferably from 40C to 140C, and the distillation is preferably carried out at a pressure of from 1 bar to 10 bar, more preferably from 2 bar to 8 bar.
1,2-Dichloroethane fraction 8 contains crude 1,2-di-chloroethane (ethylene dichloride) and can be further purified in a known manner. Fraction 8 has preferably a temperature of 30C
to 150C and a pressure of 1 to 8 bar. The by-product fraction 7 contains mainly ethyl chloride and ethylene dichloride as well as by-products such as water, vinyl chloride and perhaps trichloro-methane and non-converted ethylene. Fraction 7 preferably has a temperature of 20C to 100C and a pressure of 1 to 8 bar.
It is possible to feed by-product fraction 7 directly into the cracking reactor C in which ethyl chloride is converted into ethylene and hydrogen chloride as described above. In such a 1~9~203 case, fraction 7 is preferably preheated to a temperature of from 150C to 450C, more preferably of from 200C to 350C at a pres-sure of from 1 to 8 bar. However, it is preferred to subject fraction 7 to further fractionation steps in order to prolong the life of the catalyst in cracking step c). It is evident that the usefulness of the fractionation steps b3) and b4) described below depends on the efficiency of the fractionation step b2).
In fractionation step b3) fraction 7 is further frac-tionated into a fraction 9 which contains at least the major por-tion of 1,2-dichloroethane and trichloromethane which might remain in fraction 7 after the fractionation step b2) and into a fraction 10 which consists mainly of ethyl chloride and minor amounts of by-products ethylene, water and vinyl chloride.
The fractionation step b3) in fractionation equipment B3) is preferably carried out by distillation. The temperature of the distillation is preferably between 30C and 180C, more pre-ferably between 50C and 150C and the distillation is preferably carried out at a pressure between 1 bar and 10 bar, more prefer-ably between 2 bar and 8 bar. Fraction 9 preferably has a temper-ature of 90C to 170C, more preferably of 100C to 160C and a pressure of from 1 to 8 bar, preferably of 2 bar to 7 bar. Frac-tion 10 preferably has a temperature of 40C to 100C, more preferably of 50C to 80C and preferably a pressure of 1 to 8 bar, more preferably of 1 bar to 7 bar.
Fraction 10 can be fed into cracking reactor C. In such a case fraction 10 is preferably preheated to a temperature of X

~99203 from 150C to 450C, more preferably of from 200C to 350C at a pressure of from 1 to 8 bar. However, it is preferred to subject fraction 10 to a further fractionation step b4) in the fractiona-tion equipment B4 in order to avoid corrosion problems in the cracking reactor C).
In fractionation equipment B4, fraction 10 is separated into a liquid water phase 11, a liquid ethyl chloride phase 12 and a gaseous ethyl chloride phase 13.
The pressure in fractionation equipment B4 is preferably from 1 to 8 bar7 most preferably from 1 bar to 7 bar. The temper-ature is preferably from 20C to 100C, more preferably from 30C
to 90~C. The separation of the three phases is preferably carried out by means of gravity settling.
The liquid water phase 11 is removed from fractionation equipment B4. It preferably has a temperature of 20C to 100C
and a pressure of 1 to 8 bar. The liquid ethyl chloride phase 12 which preferably has a temperature of 20C to 100C and a pressure of 1 to 8 bar, is sent to a vaporizer. This stream is combined with the gaseous ethyl chloride phase 13 from fractionation equip-ment B4. The gaseous ethyl chloride phase preferably has atemperature of 20C to 100C and a pressure of 1 to 8 bar. The combined ethyl chloride stream 14 consists mainly of ethyl chlo-ride. The ethyl chloride stream 14 may also contain residual amounts of ethylene and vinyl chloride. The amount of vinyl chlo-ride should not exceed the limit stated above.
It is to be understood that use of the fractionation U~

~99Z03 steps bl) to b4) described with reference to the drawing is only one preferred embodiment of the fractionation step b) of the effluent 4 from the oxychlorination reactor A. It is not critical how fractionation step b) is carried out, however the ethyl chlo-ride stream 14 should contain less than 30 weight percent ethylene dichloride and vinyl chloride (total amount), based on the weight of ethyl chloride.
The ethyl chloride stream 14 is then brought into the cracking reactor C. Preferably, it is diluted with an inert dilu-ent 15 such as nitrogen. The ethyl chloride stream 14 and theinert diluent are preferably preheated to a temperature of from 150C to 450C, more preferably of from 200C to 350C at a pres-sure of from 1 to 8 bar. The cracking reaction c) is carried out as described above.
The effluent 16 from the cracking reactor C contains mainly ethylene, hydrogen chloride, inert diluent and minor amounts of by-products such as uncracked ethyl chloride. Hydrogen chloride is preferably separated from effluent 16, for example by adsorption of hydrogen chloride in washing equipment. Hydrogen chloride can be recovered as aqueous hydrochloric acid or it can be neutralised.
Preferably, effluent 16 from the cracking reactor C is then recycled to the oxychlorination step a), most preferably after having separated unreacted ethyl chloride from effluent 16.
Ethylene can be recycled to the oxychlorination step a) or to another reaction in which ethylene is consumed, for example for producing ethylene dichloride via direct chlorination of ethylene, for example as described in US patent 4,347,391.
The oxychlorination process described herein is prefer-ably a continuous process.
The present invention is further explained in the following examples which illustrate the invention but are not intended to restrict it. All parts and percentages are by weight unless otherwise specified.
Exam~le 1 A gas stream consisting of 40.9 percent ethyl chloride, 16.6 percent ethylene, 1.9 percent vinyl chloride, 0.6 percent ethylene dichloride and 40 percent nitrogen is fed to a cracking reactor C. The gas stream corresponds to the combined streams 14 and 15 in the drawing. The gas stream is preheated to 250C. The reactor is surrounded by a heat exchange jacket to maintain a temperature of 275C inside the reactor. The catalyst is gamma-alumina with a surface area of about 190 m2/g and is arranged as a fixed bed. The pressure in the reactor is maintained at 1.8 to 2 bar. The average residence time of the flowing gas stream in the cracking reactor is 15 seconds.
Cracking reactor C is operated for about 100 days. The initial ethyl chloride conversion rate is 62.7%.
Example 2 In order to evaluate the influence of vinyl chloride and ethylene dichloride on the catalyst used in cracking reaction c) a gas stream consisting of 26.7 mol percent ethyl chloride, 24 mol k percent ethylene, 47.2 mol percent nitrogen, 2.0 mol percent vinyl chloride and 0.1 mol percent ethylene dichloride is fed to the same cracking reactor C as in Example 1. The temperature, the residence time and the pressure are the same as in Example 1.
Gamma-alumina having a surface area of about 200 m2/g and a level of impurities (Na20 and Sio2) of less than 1,000 ppm is used as a catalyst. After having operated the cracking reactor for about 100 days, the ethyl chloride conversion rate is reduced to about 50 percent of its initial rate.
Example 3 Example 2 is repeated, however gamma-alumina having a surface area of about 300 m2/g and a level of impurities (Na2O and SiO2) of about 10,000 ppm is used as a catalyst. After having operated the cracking reactor for about 25 days, the ethyl chlo-ride conversion rate is reduced to about 65 percent of its initial rate.
Example 4 Example 3 is repeated, however the gas feed stream con-sists of 27.2 mol percent ethyl chloride, 24.5 mol percent ethy-lene and 48.3 mol percent nitrogen. After 50 days, the ethyl chloride conversion rate is reduced to about 65 percent of its initial rate.
Example 5 Example 2 is repeated, however the average residence time of the flowing gas stream in the cracking reactor is 30 seconds. After having operated the cracking reactor for about 100 X

1~99203 - 17a - 72425-5 days, the ethyl chloride conversion rate is reduced to about 70 percent of its initial rate.
Exameles 6 to 21 To evaluate the influence of the temperature, the pres-sure and the residence time on the ethyl chloride conversion rate, a gas stream consisting of about 27 mol percent ethyl chloride (EtCl), about 24 mol percent ethylene (C2H4) and about 49 mol percent nitrogen (N2) is heated to 250C. This stream simulates a stream obtained in the oxychlorination step a) and in fractiona-ting step b). The cracking reaction c) takes place in a reactorinto which the gas stream is continuously fed.
The results are set forth in Table I.
X

~29~203 O . .--1 ~1 ~ ~ r~ ~ ~ d' O O ~ O N 1` ~o S~--I o\ d~ O m 00 1` ~3 N ~ V;~ d 'O N O t N d ' U
a O
E~ U
o 1~ ~ O IS~ N ~ O ~ ~ r N 1-1 N ~ ~ N d' ~~ ~ (S\ N ~ ~11~ d' ~) Ul _I
; ............... .
N ~1 (~) N O ~) N ~ N r--l O ~ N N ~) r~ I r` N N 1~ t~l N u~
N ~D N O Ir~ ~1 00 ~ ~I t~) ~ O ~) L~
E~ ~OO~OOOOOOOOOOOO
~q U
:C 00~ O~1001~tr)~9 0~1--l1~ N 11 1~ ~1 O N . . . . . ... .. . . .
N ~ O N N ~l~1 0~ l N
U)d'Ci~1~1~ oIn N~) O~ ~ ~SJ ~ N Lt~
U~ Nd'd'Nd '~~SJ~ CJ~ N~ ,~
oz; - ......... - . - ..
r-l ~ N ~ ~) N O~) N ~1 N ~O~I N N
R
~_I r~ N ~ r~ O ~ ~ 0 C~ Ir1 N
Elh C)0 ~ ~ a~ ~ d'00 m In N '~Dd' ~ N t~
n~) . . .. ........
I O ~ ~ O ~ ~ O ~ O O O

'O N
a) c.) ~1 ~1 0 ~ I O _1 ~10 -1 0 0 0 ~1 ~1 --1 a) _ U Ul U~ O U~ U~ O U~ U- O Ul U~ O U~
a) ~n ~Y _ tO

a) R ~ ~ N ~ d ' U~
--E~ C:) N N N ~ ~ ~) N N N OO O N N t`~ N
N N N N N N N N N N N N N N N N
a ~D ~ ~) ~ O ~I N ~ ` CO ~ O ~l X ~ I ~I N N
~r ~s

Claims

1. An oxychlorination process for producing ethylene dichloride by a) reacting ethylene with hydrogen chloride and oxygen in the presence of an oxychlorination catalyst in an oxychlorination reactor, whereby ethyl chloride or both ethyl chloride and vinyl chloride are produced as by-products which process comprises the further steps of b) dividing, in one or more steps, the effluent from the oxychlorination reactor into at least i) an ethylene dichloride-rich fraction (I) and ii) an ethyl chloride-rich fraction (II) in such a fashion that fraction (I) contains less than 50 percent of the total weight of ethyl chloride produced in step a) and the sum of the weight of ethylene dichloride and vinyl chloride in fraction (II) is less than 30 percent of the weight of ethyl chloride in fraction (II) and c) subjecting fraction (II) to a cracking process in the presence or absence of an inert diluent whereby fraction (II) contains less than 5 percent ethylene dichloride and vinyl chloride, based on the combined weight of ethyl chloride and inert diluent in fraction (II) prior to cracking, the cracking process is carried out in the presence of a cracking catalyst in a cracking reactor and ethyl chloride is converted into ethylene and hydrogen chloride.

C-35,486-CA

2. The process as claimed in claim 1 wherein step c) is carried out at a temperature between 250°C and 320°C.

3. The process as claimed in claim 1 wherein step c) is carried out at a pressure between 1 and 8 bar.

4. The process as claimed in claim 1 wherein the residence time of ethyl chloride in the cracking reactor is from 5 to 60 seconds.

5. The process as claimed in claim 1, 2 or 3 wherein the cracking catalyst used in step c) is aluminum oxide.

6. The process as claimed in claim 5 wherein the catalyst is gamma-alumina having a surface area between 10 m2/g and 350 m2/g.

7. The process as claimed in claim 1, 2 or 3 wherein step c) is carried out in the presence of nitrogen.

8. The process as claimed in claim 1, 2 or 3 wherein the ethyl chloride-rich fraction (II) is once or twice distilled at a temperature between 30°C and 180°C at a pressure between 1 and 10 bar before carrying out step c).

9. The process as claimed in claim 1, 2 or 3 wherein water is removed from the ethyl chloride-rich fraction (II) before carrying out step c).

10. The process as claimed in claim 1, 2 or 3 wherein ethylene obtained in step c) is recycled to process step a).